1. Field of Invention
The present invention concerns loudspeaker enclosures. Even more particularly, the present invention concerns reflex folded horn speaker enclosure systems.
2. The Prior Art
The loud speaker as we know it today was invented in the 1920's. The loudspeaker basically consisted of a coil in a magnetic field electrified with alternating current which caused the coil to vibrate with an electric signal. The vibrating coil was seated in a stiff cone or diaphragm and caused the air in the cone to be in motion. This loudspeaker device is now known as a driver.
The early drivers were mounted on walls, in boxes or just hung in the open. This resulted in the sound from the drivers being "tinny." In order to improve the quality of the sound the drivers evolved to where the cone or the diaphragm itself vibrated causing the sound to radiate around the driver. This is the most common driver used today.
While the driver was evolving and improving, the enclosures, used to contain the drivers, were also evolving. The early enclosures were just that--devices to enclose or hold the drivers. When it became apparent that the enclosures also contributed to the sounds quality, enclosures that attempted to provide for the best quality of sound at each level of the music spectrum were developed.
Basically, there are three ranges or levels of the music spectrum: high-range notes, mid-range notes and low-range or bass range notes. A single driver can cover all the ranges or you can have a driver for each of the ranges. The initial trend was to have a single driver for all ranges in one enclosure. This resulted in poor sound quality in one or more of the ranges. To resolve this problem, a single enclosure for each driver was used. This resulted in needing several enclosures of varying sizes placed at critical areas around an area to provide the best sound quality. Another alternative was to install two or more drivers into one enclosure. This resulted in very large enclosures; especially where good base quality was required. The large numbers of enclosures or the large size of enclosures have drawbacks in both space usage and expense.
Recently the major improvements in the drivers have permitted improvements to be made in the enclosures, especially in reducing the size of the enclosures. However, the efforts to reduce the size of the enclosures have been unable to solve the poor quality of the bass sounds that exist in smaller loudspeaker enclosures.
A conventional driver propels sound waves forward and backward. The sound waves for the high notes are normally propelled straight forward (uni-directional). Whereas the sound waves for the lower notes tend to move or radiate in several directions (multi-directional). The multi-directional sound waves will normally overlap or cancel-out the unidirectional waves unless there is some device to separate them.
The separating device is called a baffle. The baffle is usually a flat surface device with a hole within it to mount the driver. The base of the cone of the driver is mounted to the baffle over the hole. The baffle prevents most of the multi-directional or backward sound waves from mixing with the uni-directional or forward sound waves. Each enclosure normally has a baffle.
With the baffle in place, there is a separation of the higher uni-directional sound waves from the bass multi-directional sound waves. Most loudspeaker enclosures have the high note sound waves directed to the listener with bass note sound waves being redirected in some manner back to the listener. This is known as a reflex type loudspeaker enclosure system. However, the enclosures are designed on a hit or miss basis and usually result in the bass sound waves overwhelming the listening area. The loudspeaker enclosures are commonly referred to as "boom boxes." Although these loudspeaker enclosures are reduced in size, they must still be large enough to accommodate the bass sound waves--the bigger the box the better the bass.
The air in an enclosure available for use by the bass sound waves affects the quality of the bass sound. Also, whether the enclosure is a sealed or unsealed enclosure can determine the quality of the bass sound. A small sealed enclosure with a single bass driver will usually produce a good quality bass sound. However, the loudspeaker is inefficient and restricted to one type of speaker.
What is desired is a speaker enclosure that can handle all three levels of notes efficiently and produce an excellent quality bass sound. The present invention provides a small speaker system which accommodates a multi-ranged single driver or multiple drivers, is efficient and provides a quality bass sound.